What Size Air Conditioner Do I Need for 1,200 Sq Ft?
1,200 sq ft sits on the line between 21,000 and 23,000 BTU/hr, and it is still a room-AC question.
Full breakdown: BTU per square foot.
A longer companion, using a different method, is what size AC unit for 1,000 sq ft. Keep this page on the ENERGY STAR room-AC boundary at 1,200 sq ft.
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Capacity from the chart
| Area to be cooled | Capacity needed | Source |
|---|---|---|
| 1,000 up to 1,200 sq ft | 21,000 BTU/hr | ENERGY STAR |
| 1,200 up to 1,400 sq ft | 23,000 BTU/hr | ENERGY STAR |
At this floor area the first decision is whether a room air conditioner is even the machine you are sizing. ENERGY STAR's table is titled around room air conditioners and an area to be cooled. A house or apartment whose whole conditioned area is 1,200 sq ft, served by a central system, is the load-calculation problem, not a row on this chart. If you are actually cooling one 1,200 sq ft area with room equipment, the two rows above are the published capacities.
How to size it
The rows differ by 2,000 BTU/hr. Shade on the lower row moves the target by 2,100 BTU/hr, which is slightly more than the gap, so a shaded space that correctly starts at 21,000 finishes at 18,900 BTU/hr. Do not average the two rows. The chart does not publish a capacity between them.
| Adjustment | On the 21,000 row | On the 23,000 row | Source |
|---|---|---|---|
| Heavily shaded, reduce capacity 10% | 21,000 − 10% = 18,900 BTU/hr | 23,000 − 10% = 20,700 BTU/hr | ENERGY STAR |
| Very sunny, increase capacity 10% | 21,000 + 10% = 23,100 BTU/hr | 23,000 + 10% = 25,300 BTU/hr | ENERGY STAR |
| Each additional person beyond two | 21,000 + 600 BTU/hr = 21,600 BTU/hr | 23,000 + 600 BTU/hr = 23,600 BTU/hr | ENERGY STAR |
| Unit used in a kitchen | 21,000 + 4,000 BTU/hr = 25,000 BTU/hr | 23,000 + 4,000 BTU/hr = 27,000 BTU/hr | ENERGY STAR |
10% of 21,000 BTU/hr is 2,100 BTU/hr (21,000 × 10%).
10% of 23,000 BTU/hr is 2,300 BTU/hr (23,000 × 10%).
Sunny upper row: 23,000 + 10% = 25,300 BTU/hr. One person beyond two on that upper row: 23,000 + 600 = 23,600 BTU/hr. Kitchen on the lower row: 21,000 + 4,000 = 25,000 BTU/hr. Kitchen on the upper row: 23,000 + 4,000 = 27,000 BTU/hr. The kitchen figure is for a unit used in a kitchen, which at 1,200 sq ft usually means the area includes the kitchen, not that the entire floor is a kitchen. Apply it only when that use is real.
Ceiling basis remains 8-foot. ENERGY STAR's higher-ceiling sentence still says you may want a room air conditioner with a higher CADR. It does not add a sq-ft exception at 1,200.
23,000 BTU window air conditioners on Amazon Window air conditioner support brackets on Amazon
Related questions
- What size air conditioner for 800 sq ft
- What size air conditioner for 1,500 sq ft
- What size air conditioner for 2,000 sq ft
All of these questions are listed on the topic map.
Sources
- ENERGY STAR, Room Air Conditioners — https://www.energystar.gov/products/room_air_conditioners — accessed Oct 2, 2026.
Frequently asked questions
What size air conditioner for 1,200 sq ft?
1,000 up to 1,200 sq ft is 21,000 BTU/hr, and 1,200 up to 1,400 sq ft is 23,000 BTU/hr. Heavy shade points at 21,000. A very sunny space or more than two people regularly points at 23,000.
How big is the step between those two rows?
23,000 − 21,000 = 2,000 BTU/hr. Ten percent of 21,000 is 2,100, so a shaded lower-row target is 18,900 BTU/hr. Ten percent of 23,000 is 2,300, so a sunny upper-row target is 25,300 BTU/hr.
Should a 1,200 sq ft home buy a window unit from this chart?
Only if you are sizing a room air conditioner for an area of that size. A whole-house central system should get a load calculation on the HVAC load calculator. The chart assumes an 8-foot ceiling; higher ceilings call for a higher CADR.
Where does the 1,000 sq ft guide fit?
The 1,000 sq ft AC page is a longer companion that uses a different method. It does not replace these ENERGY STAR rows. People still add 600 BTU/hr beyond two, and a kitchen still adds 4,000 BTU/hr.